90. Solar air heating
We explore DIY solar air heaters and commercial scale SolarWalls
By David Dodge and Duncan Kinney
Solar energy is a popular subject on Green Energy Futures. We’ve done stories on solar co-ops, passive solar design, solar start-ups, solar stocks, concentrated solar thermal and domestic solar hot water. And just when you think you’ve exhausted the well of solar stories we find another gem: solar air heating.
And best of all, solar air heating might be the easiest to understand and the most accessible solar technology we’ve covered yet.
Our DIY solar air heater
It’s so simple we built our own solar air heater out of found materials, pop cans and about $80 worth of materials from a local hardware store.
You can watch our video and see how it works and how we put it together; it’s definitely not rocket science. We used 70 black-painted aluminum cans, with holes drilled in the top and bottom for air circulation, under a panel of plexiglass in a ventilated wooden box. The dark metal cans are ideal solar collectors, heating air that rises inside the box. A fan at the top pushes the hot air to where want it to go.
We put our solar air heater together in the backyard of our video producer Jaro Malanowski. You don’t have to be super handy or have a lot of tools either — we did it with only a variable-speed electric drill and a small circular saw to cut the lumber for the box. And it’s not just a demonstration project; our solar air heater is being used right now. Jaro mounted it on the south-facing side of his garage and cut a hole for the ducting straight into the garage.
“When the sun hits it, it gets really hot. I’ve had it up to 52 degrees Celsius, and that hot air goes into the garage. In the summer I insulated the garage, so it’s really made a big difference — in essence it heats my garage for very little,” says Malanowski.
He can putter around in his garage in the winter, and he’s now a big believer in the technology. He wants to build an even bigger one next year, and he’s recommending it to friends and family.
“If you just have some basic skills, if you can work with an electric drill. You can even have some of your pieces cut to size at your local hardware store. It didn’t take a lot of skill at all,” says Malanowski, who’s planning to scale the idea up to a four-by-eight foot version.
SolarWall: industrial-scale solar air heating
More than 30 years ago, John Hollick of Conserval Engineering created SolarWall, a commercialized and scaled-up version of solar air heating. Holick put a modern solar air heater on Ford’s Oakville, Ontario, factory in 1990. Since then Ford has installed solar air heating systems on seven more of their plants, saving them more than $10 million in heating costs. And this technology has spread — Conserval has installed these systems in hundreds of commercial applications around the world.
SolarWall is dark exterior steel cladding placed on a south-facing wall. “There'll be thousands of tiny micro-perforations along the surface of the wall, and those perforations allow the heat that normally collects on a darker surface to be uniformly captured and then drawn into an air cavity behind. From there that air is heated, anywhere up to 50 degrees Celsius on a sunny day,” says Victoria Hollick, vice president of operations at Conserval Engineering. The building’s conventional heating and ventilation system receives the pre-heated air, which requires only a small heating boost to reach its required temperature, thus reducing the cost of heating.
SolarWall makes a lot of sense for commercial and industrial buildings because of their large heating loads and the need for fresh air for employees. By pre-heating the air before it gets into the building, owners can save an average of 20 to 30 per cent on their heating costs. Simple payback on these systems runs from five to 13 years.
But it’s not just about energy savings; improving indoor air quality is very important as well. By pre-heating your incoming air you can cycle in lots of fresh air without increasing your heating costs.
And while SolarWall got its start in the cold climates of Canada they are starting to branch out into other applications as well.
“We have projects for crop drying in California where it's being used to dry herbs and spices and coffee. We have applications in Spain and France and all over the world,” says Victoria Hollick.
Solar air heating in Canada
Whether you build a do-it-yourself model or install a SolarWall on a warehouse, solar air heating is a simple, cost-effective solution. Canadians use a ton of energy keeping themselves and their buildings warm, and solar air heating is an affordable, effective way to reduce greenhouse gas emissions and reduce the money spent on space heating with a super simple technology.
So the next time solar comes up in a conversation don’t just focus on the sexy solar panel; give a thought to the humble but effective solar air heater as well.